Here's a handy one-line Excel formula to calculate personal income tax
For the 2020-21 financial year:
=SUMPRODUCT(--(D5>={18201;45001;120001;180001}),(D5-{18200;45000;120000;180000}), {0.19;0.135;0.045;0.08})
Where: D5 = Taxable Income
For the 2019-20 financial year:
=SUMPRODUCT(--(C5>={18201;37001;90001;180001}),(C5-{18200;37000;90000;180000}), {0.19;0.135;0.045;0.08})
Where: C5 = Taxable Income
For Medicare in 2019-20 and 2020-21 we can use:
=IFS(D5>=28501,D5*0.02,AND(D5<28501,D5>22801),(D5-22801)*0.1,D5<=22801,0)
Where D5 is Taxable Income
Note: this includes the low income phase in for single individuals, but I haven't (yet) programmed in other complications such as seniors and pensioners, families and dependants. Don't forget the Medicare Levy Surcharge also!
Example spreadsheet can be found here:
https://drive.google.com/file/d/1bvaRrSjLqhJKjyg5t5kE19x1-y8-OBCm/view?usp=sharing
